Use interoperable kind for MPI_Aint.

* gfortran warns when using mpi_address_kind directly. Therefore using
  the corresponding kind from iso_c_binding removes those warnings.

configure.ac

@@ -205,6 +205,9 @@ ACX_F90_PACKAGE([MPI],[mpi],,,
 save_CFLAGS=$CFLAGS
 CFLAGS="$CFLAGS $MPI_C_INCLUDE"
 TJ_FIND_INTEGRAL_TYPE([MPI_Fint],[MPI_FINT],[@%:@include <mpi.h>])
+TJ_FIND_INTEGRAL_TYPE([MPI_Aint],[xt_mpi_aint],[@%:@include <mpi.h>])
+xt_mpi_aint_kind=c_[]AS_TR_SH([$xt_mpi_aint])
+FCFLAGS="$FCFLAGS ${FPP_DEFOPT}XT_MPI_AINT_KIND=$xt_mpi_aint_kind"
 CFLAGS=$save_CFLAGS
 AS_CASE(["$MPI_FINT"],
   [int],[XT_MPI_FINT_MAX=INT_MAX XT_MPI_FINT_FC_KIND=c_int],

src/xt_mpi_f.f90

@@ -46,11 +46,12 @@
 ! SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 !
 MODULE xt_mpi
-  USE mpi
+  USE mpi, orig_mpi_address_kind => mpi_address_kind
   USE, INTRINSIC :: ISO_C_BINDING, ONLY: c_int, c_long, c_short, c_long_long
   IMPLICIT NONE
   PUBLIC
   INTEGER, PARAMETER :: xt_mpi_fint_kind = XT_MPI_FINT_FC_KIND
+  INTEGER, PARAMETER :: mpi_address_kind = XT_MPI_AINT_KIND
   INTERFACE
     SUBROUTINE xt_mpi_comm_mark_exclusive(comm) &
          BIND(c, name='xt_mpi_comm_mark_exclusive_f2c')